<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    let num1 = Number(prompt('请输入第一个数：'))
    let num2 = Number(prompt('请输入第二个数：'))
    let sum 
    sum = num1 + num2 
    alert(`计算结果是${sum}`)
  </script>
  
</body>
</html>